[PATCH 6.4 086/800] rcu/rcuscale: Stop kfree_scale_thread thread(s) after unloading rcuscale

Greg Kroah-Hartman
2023-07-16T19:58:08Z

From: Qiuxu Zhuo <qiuxu.zhuo@intel.com>

[ Upstream commit 23fc8df26dead16687ae6eb47b0561a4a832e2f6 ]

Running the 'kfree_rcu_test' test case [1] results in a splat [2].
The root cause is the kfree_scale_thread thread(s) continue running
after unloading the rcuscale module. This commit fixes that isue by
invoking kfree_scale_cleanup() from rcu_scale_cleanup() when removing
the rcuscale module.

[1] modprobe rcuscale kfree_rcu_test=1
// After some time
rmmod rcuscale
rmmod torture

[2] BUG: unable to handle page fault for address: ffffffffc0601a87
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 11de4f067 P4D 11de4f067 PUD 11de51067 PMD 112f4d067 PTE 0
Oops: 0010 [#1] PREEMPT SMP NOPTI
CPU: 1 PID: 1798 Comm: kfree_scale_thr Not tainted 6.3.0-rc1-rcu+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
RIP: 0010:0xffffffffc0601a87
Code: Unable to access opcode bytes at 0xffffffffc0601a5d.
RSP: 0018:ffffb25bc2e57e18 EFLAGS: 00010297
RAX: 0000000000000000 RBX: ffffffffc061f0b6 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff962fd0de RDI: ffffffff962fd0de
RBP: ffffb25bc2e57ea8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000000
R13: 0000000000000000 R14: 000000000000000a R15: 00000000001c1dbe
FS: 0000000000000000(0000) GS:ffff921fa2200000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffc0601a5d CR3: 000000011de4c006 CR4: 0000000000370ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
? kvfree_call_rcu+0xf0/0x3a0
? kthread+0xf3/0x120
? kthread_complete_and_exit+0x20/0x20
? ret_from_fork+0x1f/0x30
</TASK>
Modules linked in: rfkill sunrpc ... [last unloaded: torture]
CR2: ffffffffc0601a87
---[ end trace 0000000000000000 ]---

Fixes: e6e78b004fa7 ("rcuperf: Add kfree_rcu() performance Tests")
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/rcu/rcuscale.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
index 7e8965b0827a9..d1221731c7cfd 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -797,6 +797,11 @@ rcu_scale_cleanup(void)
if (gp_exp && gp_async)
SCALEOUT_ERRSTRING("No expedited async GPs, so went with async!");

+ if (kfree_rcu_test) {
+ kfree_scale_cleanup();
+ return;
+ }
+
if (torture_cleanup_begin())
return;
if (!cur_ops) {
--
2.39.2